CyclePad

An Articulate Virtual Laboratory for Thermodynamic Cycles

CyclePad is the first articulate virtual laboratory the Qualitative
Reasoning Group has implemented. CyclePad enables students to
construct and analyze a wide variety of thermodynamic cycles. A
hypertext explanation facility provides the student with access to the
chain of reasoning underlying the derivation of each value. CyclePad
is currently being field-tested in undergraduate engineering classes
at Northwestern University, The U.S. Naval Academy, and Oxford
University.

A thermodynamic cycle is a collection of components which either
takes in heat and produces energy, or takes in work and produces some
transfer of heat, perhaps as a refrigerator or as a heat
pump. Examples of thermodynamic cycles include power plants,
refrigerators, propulsion plants, and engines. CyclePad helps you:

Specify the structure of your design , in terms of the parts of
the cycle and how they are connected together.

Analyze your design, by figuring out the consequences of
assumptions you make about it. Such assumptions include numerical
values, e.g. operating temperatures and pressures, and modeling
assumptions, e.g., whether or not to consider a turbine as isentropic.

Perform sensitivity analyses to understand how different choices
of your design contribute to its performance. For example, CyclePad
can figure out how the efficiency of a system changes as a function of
other parameters, such as a turbine inlet temperature.

CyclePad performs steady-state analyses of both open and closed
cycles. In an open-cycle, it is the components that are open to the
passage of mass through them, while in a closed cycle different
processes take place within a single component. Gas turbines are
therefore open cycles, and piston engines are closed cycles. Note that
a closed-loop steam cycle containing a boiler, turbine, condenser, and
pump is still considered to be an open cycle.

Steady-state analyses provide the kind of initial guidance needed
in conceptual design, because in the conceptual design of
thermodynamic cycles the important questions concern the operating
conditions and estimates of efficiency and cooling/heating/power
produced by the cycle. (Later stages of design concern issues such as
the response of the system to transients, developing procedures for
safe startup and shutdown, and ensuring that the system is easy to
monitor and maintain).

CyclePad works in two
phases, build mode and analyze mode. In the first phase (build), you
use a graphical editor to place components and connect them with
stuffs. Such a structure might look like this:

While you can always quit CyclePad at any time, you can only
proceed to the next phase (analysis) when CyclePad is satisfied that
your design is fully laid out, that is, when every component is
connected via some other component via stuffs, and every stuff has
been used as both an input and an output for components in the
design. Once your design is laid out, the real fun begins--the
analysis phase.

In the analysis phase, you specify:

What working fluid you are using.

What modeling assumptions you wish to make in analyzing your
design.

Numerical values for the properties of components and stuffs

As soon as you give CyclePad some information, it draws as many
conclusions as it can about your design, based on everything you have
told it so far. When you specify a working fluid, for instance, it
knows whether to use property tables or an ideal gas
approximation. When you specify numerical values, CyclePad sees if it
can then calculate other numerical values. It displays the results of
its calculations, and you are free to inquire about how values were
derived and how one might proceed at any time, using a hypertext query
system.

As you provide more information, CyclePad deduces more about the
physical system. Eventually, you may have filled in all of the
relevant information about the cycle, so that you have numerical
values for properties such as the coefficient of performance (if you
are designing a refrigerator), the thermal efficiency (if you are
designing a heat engine), or other properties of interest such as the
total amount of work produced or consumed by the cycle. How far you go
is up to you. At any time you can save your design to a file so that
you can continue working on it later, and generate reports describing
the state of your analysis of the design.

CyclePad also supports sensitivity analyses. For instance, suppose
you wanted to understand how the thermal efficiency of the cycle
varies as a function of the efficiency of a compressor or some other
component. Such analyses are quite tedious to do by hand, but CyclePad
makes them quite easy and will generate such information for you in
graphical form.

"Common Lisp remains one of the best languages for Artificial
Intelligence applications, its flexibility enables rapid
experimentation and deployment", said Professor Ken Forbus, Walter
P. Murphy Professor of Computer Science at Northwestern
University. "Today's Lisp compilers are robust and flexible allowing
development entirely within Lisp or in combination with other
languages. For example, our CyclePad system is written entirely in Allegro
CL. Similarly, our sketch understanding system, CogSketch, which is a
novel platform for both cognitive science research and education is
primarily written in Allegro CL with two modules in C."

You can download CyclePad for free here. For additional informaiton on the CyclePad
Project, see here.

About Ken Forbus

Ken Forbus, the project leader, is the Walter
P. Murphy Professor of Computer Science and Professor of Education at
Northwestern University. He is notable for his work in qualitative
process theory, automated sketch understanding and on automated
analogical reasoning. He developed the structure mapping engine based
on the structure-mapping theory of Dedre Gentner. He is a Fellow of
the Association for the Advancement of Artificial Intelligence. He is
the Chair-elect of the Cognitive Science Society and became the chair
(president) of the society in August, 2011.